A planar heat-generator like a heat-generating film (or heat-generating sheet) can be applied to various uses such as a vehicle heat-generating sheet, stroller heat-generating sheet or portable heat-generating products.
A representative use to which the planar heat-generator is applied is a vehicle heat-generating sheet. In order to apply the planar heat-generator to the vehicle heat-generating sheet, the heat-generator should be capable of operating at a low voltage or low power with respect to the energy efficiency, and should have a good flexibility. Further, when the seat is occupied, the heat-generator should fit to a body curve of a sitter (hereinafter, sometimes depicted as ┌filling property)), be easily bent 3-dimensionally, and exhibit a soft buffer action so as to feel comfort (hereinafter, sometimes depicted as ┌comfort property)).
As the said heat-generating film or heat-generating sheet, a product wherein both sides of a wire-shape heat-generating material are wrapped with a non-woven fabric has been in use.
However, in case of the existing heat-generating product which has non-woven fabric attached to the both sides of the
As shown in FIG. 2, in the heat-generating film (1) of the present invention, one or more heat-generating parts (12a, 12b, 12c and the like) which exist on the base sheet (11) by being patterned in a linear configuration in one direction (for example, widthwise direction of the base sheet) can be parallelly arranged separately to each other in the heat-generating layer. As shown in FIG. 2, the said heat-generating part may be formed in multiple parts in the present invention, and a single heat-generating part can be formed solely under certain circumstances. Hereinafter, the terms ┌widthwise direction┘ and ┌longitudinal direction┘ used herein are relative concepts, for example, if a direction which is parallel to any one side of the base sheet is defined as ┌widthwise direction┘, a direction which is perpendicular to the said ┌widthwise direction┘ can be defined as ┌longitudinal direction┘. Further, in case that the base sheet has not only a square or rectangular configuration but also a circular, elliptical, polygonal or amorphous configuration in the present invention, if the heat-generating part is formed parallel to a certain direction on the base sheet, the direction is defined as the ┌widthwise direction┘, and the direction which is perpendicular thereto is defined as the ┌longitudinal direction┘.
In the present invention, it is preferred that the heat-generating part (12a, 12b, 12c and the like) included in the heat-generating layer is patterned to a configuration having a prescribed rule on the base sheet in relation to low voltage driving quality. heat-generating material, there is a problem that higher output power should be provided due to the heat loss caused by insulation. Further, in the wire type product, the wire length should be elongated, and the wires of a back plate and cushion should be connected to direct current to offer higher resistance. If disconnection or shortage of the wire occurs at any part of the product having a direct current structure, product defects may be caused.
In order to complement these defects of the wire product, there is a known product which uses a carbon-coated wire as the heat-generating material. However, the carbon can't be uniformly coated on the said product, and therefore can't solve the regional heat generating problem.
Further, in case of a planar heat-generator using carbon, when it is applied to the vehicle sheet, the comfort property and filling property are not sufficient because it is not easy to bend the film and is difficult to reduce the thickness. Further, if carbon is used as the heat-generating material, large resistance change is generated by physical impacts such as continuous bending. Further, in case of a carbon material, an amount of the material should increase to convert kinetic energy of electrons to heat energy, and therefore low voltage heat-generation is not possible.